Optics Question 684

Question: At what distance from a convex lens of focal length 30 cm, an object should be placed so that the size of the image be 1/2 of the object

[J&K CET 2004]

Options:

A) 30 cm

B) 60 cm

C) 15 cm

D) 90 cm

Show Answer

Answer:

Correct Answer: D

Solution:

$ m=-\frac{1}{2} $

$ \therefore m=\frac{f}{u+f} $

$ \Rightarrow -\frac{1}{2}=\frac{30}{u+30} $

$ \Rightarrow u=-90cm $



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